Method for biologically removing nitrogen from wastewater
First Claim
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1. An activated sludge process for biologically removing BOD and nitrogen from wastewater comprising the steps of:
- (a) forming mixed liquor;
(b) transferring the mixed liquor through a first nitrogen removal stage by directing the mixed liquor into and through first anoxic and aerobic treatment zones including maintaining the mixed liquor under anoxic conditions within the first treatment zone for a specified period to permit denitrifying organisms to reduce a portion of the nitrates and nitrites present in the mixed liquor to elemental nitrogen, transferring a portion of the mixed liquor from the first anoxic zone to the first aerobic zone and aerating the mixed liquor for a sufficient time period for nitrifying organisms to convert a portion of the ammonia and organic nitrogen in the mixed liquor into nitrates and nitrites, and circulating the mixed liquor back and forth between the first anoxic zone and the first aerobic zone of the first nitrogen removal stage to effectuate denitrification and nitrification;
(c) transferring mixed liquor from the first nitrogen removal stage to a second nitrogen removal stage having a second anoxic zone and a second aerobic zone, and circulating the mixed liquor back and forth between the second anoxic zone and the second aerobic zone of the second stage to effectuate further denitrification and nitrification;
(d) transferring the mixed liquor treated in the first and second nitrogen removal stages to a final clarifier where settled sludge is separated from purified supernatant; and
(e) recycling at least a portion of the settled sludge to form the mixed liquor.
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Abstract
The present invention relates to a system and method for biologically removing nitrogen from wastewater. Both the system and method entails forming a mixed liquor and transferring the mixed liquor to a series of nitrogen removal stages. Each nitrogen removal stage includes both anoxic and aerobic treatment zones. Mixed liquor is recycled back and forth between the anoxic and aerobic treatment zone of each stage. Because of this basic flow scheme, the process gives rise to a high reactor rate and highly efficient nitrogen removal process.
71 Citations
21 Claims
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1. An activated sludge process for biologically removing BOD and nitrogen from wastewater comprising the steps of:
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(a) forming mixed liquor; (b) transferring the mixed liquor through a first nitrogen removal stage by directing the mixed liquor into and through first anoxic and aerobic treatment zones including maintaining the mixed liquor under anoxic conditions within the first treatment zone for a specified period to permit denitrifying organisms to reduce a portion of the nitrates and nitrites present in the mixed liquor to elemental nitrogen, transferring a portion of the mixed liquor from the first anoxic zone to the first aerobic zone and aerating the mixed liquor for a sufficient time period for nitrifying organisms to convert a portion of the ammonia and organic nitrogen in the mixed liquor into nitrates and nitrites, and circulating the mixed liquor back and forth between the first anoxic zone and the first aerobic zone of the first nitrogen removal stage to effectuate denitrification and nitrification; (c) transferring mixed liquor from the first nitrogen removal stage to a second nitrogen removal stage having a second anoxic zone and a second aerobic zone, and circulating the mixed liquor back and forth between the second anoxic zone and the second aerobic zone of the second stage to effectuate further denitrification and nitrification; (d) transferring the mixed liquor treated in the first and second nitrogen removal stages to a final clarifier where settled sludge is separated from purified supernatant; and (e) recycling at least a portion of the settled sludge to form the mixed liquor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. An activated sludge process for biologically removing BOD and nitrogen from wastewater comprising the steps of:
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(a) forming mixed liquor; (b) transferring the mixed liquor through a plurality of nitrogen removal stages by directing the mixed liquor into a first anoxic zone of a first nitrogen removal stage and maintaining the mixed liquor under anoxic conditions for a specified period to permit denitrifying organisms to reduce a portion of the nitrates and nitrites present in the mixed liquor to elemental nitrogen, transferring a portion of the mixed liquor from the first anoxic zone to a first aerobic zone in the first nitrogen removal stage and aerating the mixed liquor for a sufficient time period for nitrifying organisms to convert a portion of the ammonia and organic nitrogen in the mixed liquor into nitrates and nitrites, and recycling the mixed liquor back and forth between the first anoxic zone and the first aerobic zone of the first nitrogen removal stage to effectuate denitrification and nitrification; (c) transferring mixed liquor from the first anoxic zone to a second anoxic zone of a second nitrogen removal stage and denitrifying the mixed liquor, transferring the mixed liquor from the second anoxic zone to a second aerobic zone and nitrifying the mixed liquor within the second aerobic zone, and recycling the mixed liquor back and forth between the second anoxic zone and the second aerobic zone of the second stage to effectuate further denitrification and nitrification; (d) transferring the mixed liquor treated in the first and second nitrogen removal stages to a final clarifier where settled sludge is separated from purified supernatant; and (e) recycling at least a portion of the settled sludge to form the mixed liquor.
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21. An activated sludge process for biologically removing BOD and nitrogen from wastewater comprising the steps of:
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(a) forming mixed liquor; (b) transferring the mixed liquor through a series of nitrogen removal stages by directing the mixed liquor into a first anoxic zone of a first nitrogen removal stage and maintaining the mixed liquor under anoxic conditions for a specified period to permit denitrifying organisms to reduce a portion of the nitrates and nitrites present in the mixed liquor to elemental nitrogen, transferring a portion of the mixed liquor from the first anoxic zone to a first aerobic zone within the first nitrogen removal stage and aerating the mixed liquor for a sufficient time period for nitrifying organisms to convert a portion of the ammonia and organic nitrogen in the mixed liquor into nitrates and nitrites, and recycling the mixed liquor back and forth between the first anoxic zone and the first aerobic zone of the first nitrogen removal stage to effectuate denitrification and nitrification; (c) transferring mixed liquor from the first aerobic zone to a second aerobic zone of a second nitrogen removal stage and nitrifying the mixed liquor therein, transferring the mixed liquor from the second aerobic zone to a second anoxic zone within the second nitrogen removal zone and denitrifying the mixed liquor in the second anoxic zone, and recycling the mixed liquor back and forth between the second aerobic zone and the second anoxic zone of the second stage to effectuate further nitrification and denitrification; (d) transferring the mixed liquor treated in the first and second nitrogen removal stages to a final clarifier where settled sludge is separated from purified supernatant; and (e) recycling at least a portion of the settled sludge to form the mixed liquor.
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Specification